Science Experiment: Chemical Reaction – Penny Cleaner

Everything in the universe is made of teeny tiny particles called atoms. Some things are made up of just one kind of atom. A penny is made up entirely of copper atoms. Atoms can join together to make molecules. When a penny is exposed to oxygen in the air, the copper atoms of the penny and the oxygen atoms in the air combine. A chemical reactiontakes place that makes a molecule called copper oxide – that is the dirty stuff that you see on the penny. This “stuff” is often referred to as “tarnish.” When you soak the pennies in taco sauce, another chemical reactiontakes place. Try this experiment to watch this chemical reaction.

You Will Need:

Dirty Pennies

Taco Sauce

Vinegar

Tomato Paste

Salt

Water

Small Plates

Masking Tape

Put some tarnished pennies in a small dish and pour taco sauce over them. Let the taco sauce sit for a few minutes and then wash the taco sauce off the pennies. How do the pennies look now? If you look at the ingredients in the taco sauce you will notice that the main ingredients are tomato paste, vinegar and salt. Which ingredient affected the tarnish on the pennies? To find out, you need to test different combinations of the ingredients. First, try to polish the pennies with just tomato paste, just salt and just vinegar. How do the pennies look? Then, try polishing the pennies in different combinations of the ingredients: tomato paste + salt, vinegar + salt and tomato paste + vinegar. Which combination worked best?

Here are some websites that will give you good directions for this experiment and an explanation of the chemical reaction that creates the tarnish and then takes it away again: